What the Biggest Loser Study Shows Us About Losing Weight—and Keeping It Off

Pete Thomas was in bad shape the night before he stepped on stage for his first official weigh-in on NBC’s The Biggest Loser. It was 2005, and he weighed just over 400 pounds. His blood pressure was high, his body fat percentage was 51, and the show’s doctors had diagnosed him with type 2 diabetes in a preliminary physical. “They said I should be on insulin,” he recalls.

In the first two months, Thomas dropped 83 pounds. He maintained a grueling exercise regimen even after he was voted off the show midseason: 2½ hours of exercise a day, all while working full time and consuming between 1,600 and 2,500 calories. By the end of the season, he had lost another 102 pounds—over 45 percent of his body weight in all, enough to claim a $100,000 prize.

Since its premiere in 2004, The Biggest Loser has become a cultural phenomenon. Its attention-grabbing format turns weight loss into a competitive event: Teams of contestants, isolated on a ranch in California, work to shed pounds over the course of several months. Each week, competitors are eliminated or voted off the show by other contestants. At the end of the season, the winners—or “Biggest Losers”—get cash prizes.

For Thomas, the benefits of the show went beyond weight loss and cash: His high blood pressure returned to normal, and within weeks of starting the strict diet and exercise regime, his blood glucose was in the non-diabetes range.

But Thomas says the real struggle started the day the show wrapped and he was faced with the challenge of keeping those pounds off. “The Biggest Loser is a weight-loss show, not a weight-loss maintenance show,” Thomas says. “When you have struggled with obesity for your entire life, you’re not going to solve the problem in three months, or six months, or a year.”

TV Drama

In 2008, National Institute of Diabetes and Digestive and Kidney Diseases researcher Kevin Hall, PhD, saw an episode of The Biggest Loser. The metabolism expert was intrigued to see obese contestants running on treadmills, lifting weights, and reshaping their bodies over the course of just a few months. “I saw people losing dramatic amounts of weight in a short period of time,” he recalls. “I wondered what was happening—not just to their body weight, but to their metabolism during that time.”

After contacting the show’s producers, Hall sent a postdoctoral fellow from his lab to the Biggest Loser ranch in Malibu, just before the start of the show’s eighth season in 2009. There, the contestants were weighed and their body fat percentages and resting metabolic rates (which indicate how many calories their bodies burned when they were not moving) were measured. More measurements were taken six weeks into the show and after the final weigh-in.

Six years later, Hall brought 14 contestants from Season 8 to his lab in Maryland for another set of exams. He wanted to know if their bodies’ energy requirements had changed as a result of the show and how weight loss impacted their metabolism over the long term.

Converting Calories

So what is metabolism? It’s a key question for physiology experts and scientists who study weight loss. Put simply, it’s the conversion of food and oxygen into life-sustaining energy. Every minute of the day, your body is hard at work converting food, water, and oxygen into energy. That energy repairs and replaces damaged cells, keeps your heart beating and lungs breathing, and fuels your strength to get out of bed and to walk down the street.

Everyone has a metabolic “set point” based on how much energy their body requires. The set point is the number of calories you need to consume to break even each day, covering the energy your organs need to function and what you need to move around. Take in more calories than you expend, and your body will try to store them in the form of fat, leading to weight gain. Take in fewer, and the body responds by burning fat reserves, leading to weight loss.

Your metabolic rate, together with appetite and feelings of hunger, determines the weight you can maintain without working at it. For most people, it changes slightly over time—a man in his 20s will be able to eat a little bit more without gaining weight than the same fellow 50 years later—but a person’s stasis body weight is fairly fixed. And weight loss research shows that the body fights fiercely to keep itself at that weight.

A person’s weight set point depends on different factors, such as lifestyle and environment. A large component is genetic; some people are heavier by nature. Evolutionary biologists use the term “thrifty gene” as shorthand for a genetic propensity for slow metabolism.

Born This Way

What is slow metabolism? Researchers think that the ability to slow down metabolism may have helped early humans make it through periods of famine. When food was scarce, people would respond by using less energy, conserving precious resources and surviving on reserves of fat. But the same thrifty genes thathelped our distant ancestors hang onin lean times turned out to be a disaster in an age of supermarkets, fast food, sedentary office jobs, and long car commutes.

While Americans aren’t substantially different genetically from people a generation or two ago—genes take thousands of years to change—they are, on average, 25 pounds heavier now than they were 35 years ago. “It’s very new for humankind to be in an environment of abundance,” says Eric Ravussin, PhD, a researcher at the Pennington Biomedical Research Center in Baton Rouge, Louisiana, who was not involved with the study. “The environment has really triggered this epidemic of obesity.”

What was surprising about the Biggest Loser contestants who took part in Hall’s study was that even when excess calories were already stored in the form of fat, their bodies still responded by slowing metabolism as if they were starving. As they lost weight, their bodies adapted, finding ways to get the most out of each calorie. “After weight loss, people need to be extra vigilant by increasing their energy expenditure more than they may expect,” says Jeff Horowitz, PhD, an exercise physiologist at the University of Michigan who was not involved with the study. That means being more physically active, whether through exercise or simply moving your body more.

For decades, researchers have searched for a way to short-circuit slower metabolism—a pill, for example, that would prompt the body to burn fat faster. Nothing they’ve come up with so far has been effective and safe. “We know there are drugs that affect the pathways regulating energy metabolism, like nicotine, amphetamines, and thyroid hormones,” says Ravussin. “All of them are dangerous.”

The more mundane alternatives are frustratingly familiar to anyone who’s ever thought about losing weight: diet and exercise, weight loss medications in combination with diet and exercise, or surgery in more extreme cases.

Mystery Spot

You might think that metabolism would be a pretty simple equation: X pounds = Y calories each day. But that mysterious metabolic set point can vary tremendously from person to person, based on genetics and lifestyle.

Because muscle mass and the body’s internal organs are the biggest calorie-burners we have, Hall didn’t expect lost fat to play much of a role in the participants’ daily calorie needs—the muscles and organs stayed the same. For Biggest Loser contestants who lost fat but kept (or even added) muscle, conventional wisdom says that their daily calorie requirements should stay relatively stable even after their weight loss.

The results six years later were shocking: The contestants had regained substantial amounts of weight but were still burning far fewer calories than they were before they started the show. Their metabolisms had slowed so dramatically that they could not maintain their thinner bodies, suggesting the body somehow dials down the calorie needs of muscle and organs to make it possible to gain fat.

As contestants lost weight, their bodies adapted and ran on fewer calories each day. In other words, when Season 8 winner Danny Cahill dropped 239 pounds on the show, his metabolism dropped, too. At his season-winning weight of 191 pounds, Cahill’s body burned approximately 800 fewer calories per day than the average 200-pound individual.

“Despite folks doing all this exercise and preserving fat-free mass, their metabolic rate fell many hundreds of calories a day,” Hall says. “The bigger the change in lifestyle, the stronger the metabolic adaptation.”

Permanent Change

The findings, published in the journal Obesity in May, made a huge splash. They were featured on the front page of the New York Times and dozens of other media outlets. Some experts saw the study as proof that exercise and diet can work. For people hoping a short-term diet might lead to long-term weight loss, though, the message seemed discouraging: There’s no light at the end of the tunnel, just a lifetime of less food and more exercise. “It’s a mistake to think you can quit or relax once you’ve reached your goal,” Hall acknowledges. “You have to treat it as a permanent lifestyle change to counteract these drivers.”

The Biggest Loser study may help dispel a weight loss myth common in our culture: that obesity is the result of laziness or lack of determination. Hall says that’s unfair, and in light of his data, demonstrably untrue.

Biggest Loser contestants, Hall points out, volunteer to spend months isolated on a ranch, running on treadmills for hours a day and eating a severely restricted diet.

And yet even these extremely motivated individuals have trouble keeping weight off. “No one can accuse these folks of being lazy or lacking willpower,” Hall says. “These folks had a biological adaptation that resisted weight loss, and promoted weight regain.”

The study’s findings may have surprised researchers, but they didn’t shock dieters, who know all too well that long-term weight loss is extremely difficult to maintain over the years.

A Focus on Weight

Of the 14 Biggest Loser contestants who participated in Hall’s study, all but one regained weight. Four now weigh more than they did at the beginning of the show. Cahill, who won $250,000 for his dramatic weight loss, has regained 100 pounds.

The study raises an interesting question about the payoff and pitfalls of extreme diet and exercise for weight loss. Some researchers worry The Biggest Loser’s focus on dramatic weight loss could discourage or intimidate the average person. Michelle Segar, PhD, MPH, a University of Michigan psychologist who studies motivation, wrote No Sweat: How the Simple Science of Motivation Can Bring You a Lifetime of Fitness. She says the show “reinforces and magnifies our culture’s obsession with weight. We would be better off getting people focused on how they feel from the choices they make.”

Remember the lone Season 8 participant in Hall’s study who didn’t regain weight? That was Erinn Egbert, now 29. At the time of the show, she was a college student at Ohio State University. She decided to try out for The Biggest Loser, in part, because of a family history of type 2 diabetes. “I wanted to start preventive measures early,” she says.

In a twist, the show’s creators gave viewers at the end of Season 7 the chance to choose between two possible contestants to go to the Biggest Loser ranch the following season. Egbert was the one who stayed home.

Succeeding at Home

That, Egbert says now, made all the difference. She got coaching and made a brief cameo on the show, but otherwise she had to find ways to stay motivated. “I had to teach myself everything. I had to live it every day,” she says. “I think that had an impact on why I was successful.”

When the season was over, Egbert had lost 70 pounds from her starting weight of 240. She kept dropping pounds after the show, reaching 130 at one point.

Egbert says her experience is proof sustainable weight loss is possible outside the context of a TV reality show. “The problem is they don’t give you any insight on how to maintain [weight loss],” she says.

Other researchers point out that the dramatic weight loss seen on the show isn’t necessary to improve health, particularly for people with prediabetes and type 2 diabetes. “Weight loss of 5 to 10 percent equals a tremendous improvement in metabolic health and is enough to improve insulin sensitivity,” Ravussin says.

Not long after the study came out, Mayo Clinic exercise physiology expert Michael Joyner, MD, wrote a blog post: “As crazy as the weight-loss program from The Biggest Loser TV program seems, it actually worked very well over time compared with the alternatives.”

By contrast, nationwide studies have shown that just 1 in 7 Americans have managed to lose 10 percent of their weight and keep it off long term. By that measure, the Biggest Loser contestants are actually above average, Joyner says.

As a group, the Season 8 contestants maintained an average 12 percent weight loss over the course of six years—a result that’s comparable to dramatic steps like gastric bypass surgery.

The Biggest Loser study results are a powerful argument in favor of lifestyle change—either moderate or extreme—as a weight-loss strategy. “We give up on exercise way too quickly. People can and do reengineer their lives and keep off weight,” Joyner says.

Lasting Results

Part of the problem for many people struggling to keep weight off may lie in the different definitions of “diet.” Most people think of a diet as a one-off effort to slim down. Once their weight-loss goal is met, the diet is over.

“The idea that … you can go back to eating hamburgers and french fries and pizza is wrong,” Thomas says. “You can’t think like that.”

Indeed, when dietitians and doctors recommend diet and exercise to people with diabetes or prediabetes, they’re talking about something much broader—and longer lasting. “Diet is what youeat, not this short-term thing,” says Horowitz.

Egbert says that losing weight is the easy part. “Maintaining is the hard part. If you go back to the way you were living before, you’re setting yourself up for disaster.”

Lifestyle revamp

When his time on the show was over, Thomas realized he had to treat eating as an addiction. He read everything he could on the science of weight loss and behavior change. It took him years to develop the habits he needed to stay thin, but he’s maintained his weight loss for over a decade.

In 2012, Thomas wrote a book called Lose It Fast, Lose It Forever: A 4-Step Permanent Weight-Loss Plan from the Most Successful Biggest Loser of All Time. There was no magic bullet, just hard-won advice: Make exercise and a healthy diet regular parts of your daily routine, and approach overeating as a mental as well as physical problem.

Thomas says that creating support networks was particularly helpful. “If you can set up a pattern of lifestyle change, you will be successful,” he says. You will fail, he says, if you think you can maintain weight loss entirely on your own.

Egbert has turned to social media for support. Now a Beach Body coach based in Fort Wayne, Indiana, she says chronicling her efforts to stay thin via Instagram has been a powerful motivator. But when her online followers come to her for coaching, she cautions them. “People want that instant gratification,” she says. “I make it a point to tell them [that] this is a process.”